Latest exam Aptitude Question SOLUTION: I need to factor and I do not understand this equation, please help 3a^2(a-b)-6a(a-b)+21(a-b) 1)3(a-b)(a^2-2a+7) 2)(3a-b)(a^2-2a+7) 3)(a-b)(3a^2-6a+21) 4)3(a-b)(a^2-6a+21)